Precision air conditioner with an indirect evaporative unit

ABSTRACT

The present invention relates to a precision air conditioner with an indirect evaporative unit, which comprises a gas-gas heat exchanger, an external circulation fan, an internal circulation fan, a gas filter module, a gas humidification module, an evaporator, a condenser, a condenser fan, a compressor and an air conditioner enclosure. The combination of indirect evaporative cooling and mechanical refrigeration enables indirect evaporative cooling to operate all year round with high air conditioning and refrigeration efficiency. During summer, mechanical refrigeration is used for secondary cooling to achieve the desired temperature. Further, the condenser of the precision air conditioner is upgraded to an indirect evaporative condenser, and the mechanical refrigeration efficiency can be greatly improved.

RELATED APPLICATION

The present application claims priority to Chinese Patent ApplicationNo. 201711379371.5, filed on Dec. 20, 2017, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to the technical field of precision airconditioners, and more particularly to a precision air conditioner withan indirect evaporative unit for a data center.

BACKGROUND OF THE INVENTION

After decades of development, the precision air conditioner technologyis mature in all aspects. Due to its ease of use, simple operation andhigh reliability, the precision air conditioner is widely used in smalland medium data centers and other applications where the temperature andhumidity requirements are relatively strict. The main problem of theproducts is the low coefficient of performance (COP), which will lead toa narrower application of such products if no revolutionary innovationis made.

The cooling and refrigeration are required for the data centersthroughout the year. Generally, the standard temperature and humidityfor the data centers are set at 23±1° C. and 50±10%, respectively. Thehot air generated from the data center is at a temperature of 35-44° C.Meanwhile, the highest wet bulb temperature is under 30° C. in China.Thus, it is possible to cool the data center using the exterior lowtemperature cold source by means of ventilation or heat exchange. Fromthis point of view, it can be seen that the exterior cold source can betheoretically used to cool the hot air exhausted from the serverthroughout the year. However, in practice, the use of exterior coldsources cannot be maintained for a whole year, either by direct use offresh air or the use of indirect evaporative cooling alone.

In the case where precision air conditioner is utilized alone, only alow COP can be obtained. In the case where fresh air is utilized alone,conventional treatment methods may not achieve the expected results dueto poor domestic air quality. Further, fresh air can only be utilizedfor a relatively short period of time. The indirect evaporative coolingmay extend the time period when the exterior cold sources is utilized.In much of northern China, compressors are used for mechanicalrefrigeration in less than three months a year. However, there are stillmany problems with the way it combines with a traditional airconditioner.

Due to the poor domestic air quality, indirect evaporative coolingequipment that normally operates in foreign countries will encounter alot of troubles in China. For example, dust removal and heat exchangercleaning require manual treatment, which not only brings a lot of manualwork but also cause the equipment to change from working state to themaintenance state.

SUMMARY OF THE INVENTION

Based on the above technical problems, provided is a new precision airconditioner with an indirect evaporative unit, which can make theindirect evaporative cooling working all year round and achieve highcoefficient of performance by combining indirect evaporative coolingtechnology and mechanical refrigeration technology. In summer, theprecision air conditioner only needs mechanical refrigeration as asecondary cooling to achieve the desired temperature. Further, in suchprecision air conditioner, the condenser of the precision airconditioner is upgraded to an indirect evaporative condenser, and themechanical refrigeration efficiency can be greatly improved.

The technical solution of the present invention will be described asfollows.

A precision air conditioner with an indirect evaporative unitcomprising: a gas-gas heat exchanger, an external circulation fan, aninternal circulation fan, a gas filter module, a gas humidificationmodule, an evaporator, a condenser, a condenser fan, a compressor, anair conditioner enclosure.

The gas-gas heat exchanger is provided with a heat exchanger internalcirculation air inlet, a heat exchanger internal circulation air outlet,a heat exchanger external circulation air inlet, a heat exchangerexternal circulation air outlet, a heat exchanger internal circulationpassage, and a heat exchanger external circulation passage, heatexchanger plates. The gas-gas heat exchanger is a type of gas-gas heatexchanger having dividing walls. The heat exchanger plates are arrangedto be spaced to form the heat exchanger internal circulation passage andthe heat exchanger external circulation passage. Heat is transferredbetween external air and internal air through the heat exchanger platesof the gas-gas heat exchanger.

The air conditioner enclosure is arranged around the precision airconditioner with an indirect evaporative unit. The air conditionerenclosure is provided with an internal circulation air inlet, aninternal circulation air exhaust passage, an external circulation airinlet, an external circulation air intake passage, and an externalcirculation air exhaust passage.

The internal circulation air inlet is connected to the heat exchangerinternal circulation air inlet, and the external circulation air intakepassage is connected to the heat exchanger external circulation airinlet.

The external circulation fan is arranged above the gas-gas heatexchanger.

The internal circulation fan is arranged below the gas-gas heatexchanger.

The gas filter module, which is connected with the external circulationair inlet, is arranged in the external circulation air intake passage.The gas filter module is arranged perpendicularly or substantiallyperpendicularly.

The gas humidification module is arranged between the gas filter moduleand the gas-gas heat exchanger.

The evaporator is arranged in the internal circulation air exhaustpassage below the gas-gas heat exchanger.

The condenser is arranged below or above the external circulation airintake passage and communicates with the external circulation air intakepassage.

The condenser fan is arranged below or above the condenser.

The compressor is connected to the evaporator and the condenser.

The precision air conditioner with an indirect evaporative unit has acomplete external air circulation as follows. The external air goesthrough the gas filter module and enters the external circulation airintake passage, and then enters the heat exchanger external circulationpassage after being humidified by the gas humidification module. Heat istransferred between the external air and the internal air flowing in theheat exchanger internal circulation passage through the heat exchangerplates, and then the external air enters the external circulation airexhaust passage, and then is exhausted to the exterior by the externalcirculation fan.

The precision air conditioner with an indirect evaporative unit has acomplete internal air circulation as follows. The internal air entersthe heat changer internal circulation passage from the internalcirculation air inlet. Heat is transferred between the internal air andthe external air flowing in the heat exchanger external circulationpassage through the heat exchanger plates. The internal air goes throughthe evaporator and then is cooled. The internal air then enters theinternal circulation air exhaust passage, and then is exhausted to theinterior by the internal circulation fan.

The precision air conditioner with an indirect evaporative unit has acomplete condenser cooling gas-circulation as follows. The external airgoes through the gas filter module and enters the external circulationair intake passage, and then enters the condenser after being humidifiedby the humidification module. Heat is transferred between the externalair and the condenser, and then the external air is exhausted to theexterior by the condenser fan.

In another embodiment, the gas-gas heat exchanger is a cuboid having arectangular cross section. The heat exchanger external circulation airoutlet is arranged on the top of the gas-gas heat exchanger. The heatexchanger internal circulation air outlet is arranged on the bottom ofthe gas-gas heat exchanger. The heat exchanger external circulation airinlet is arranged at the bottom-right corner of the gas-gas heatexchanger. The heat exchanger internal circulation air inlet is arrangedat the top-left corner of the gas-gas heat exchanger.

In another embodiment, the gas-gas heat exchanger has a hexagonal crosssection. The heat exchanger employs a counter-flow arrangement in themiddle portion and a cross-flow arrangement at the inlet or outlet forthe external air and the internal air.

In another embodiment, the gas-gas heat exchanger has a pentagonal crosssection. The heat exchanger employs a counter-flow arrangement in themiddle portion and a cross-flow arrangement at the inlet or outlet forthe external air and the internal air.

In another embodiment, the gas-gas heat exchanger has a cross section ofa combination of two quadrangles. The heat exchanger employs across-flow arrangement in the middle portion and at the inlet or outletfor the external air and the internal air.

In another embodiment, a cleaning nozzle to spray liquid is arrangedinside the heat exchanger.

In another embodiment, the gas filter module comprises an automatic dustremoval assembly for periodically removing dust from a filter screen.

In another embodiment, the gas humidification module further comprises avariable-frequency water pump, wherein water pressure is adjusted byadjusting working load of the variable-frequency water pump during theoperation of the air conditioning system. The gas humidification modulefurther comprises a plurality of sets of nozzles, each of whichcorresponds to a specific start-up pressure. The nozzle will work whenthe pressure is greater than or equal to the start-up pressure of thecorresponding nozzle.

In another embodiment, the external circulation air exhaust passage ofthe air conditioner enclosure is curved, and the external circulationair is distributed to both sides of the air conditioner enclosure andexhausted to the exterior.

In another embodiment, the internal circulation fan and the externalcirculation fan are centrifugal electronically commutated fans. The flowdirection changes by 90 degrees or nearly 90 degrees after the airpasses through the fan.

The present invention has the following advantages.

The present invention provides a new apparatus by combining two ways ofcooling, including mechanical refrigeration and indirect evaporativecooling. The apparatus may cool the air exhausted from the server bymeans of indirect evaporative cooling in spring, autumn and winter. Insummer, indirect evaporative cooling is employed for preliminarycooling, and mechanical cooling is employed to cool the air if the airdoes not reach the expected 23° C., thus saving energy. It would bepossible for the data centers in most of the area north of the YangtzeRiver in China that the compressor runs no more than 3 months, whichwill greatly improve the energy efficiency throughout the year. Inaddition, in summer when the variable-frequency compressor operates, themechanical refrigeration efficiency may be greatly improved due to thelow-load operation of the compressor and the use of indirect evaporativecondenser. The present invention provides a design of a new gas-gas heatexchanger with automatic cleaning function. The present inventionfurther provides a design of an automatic dust removal device, which canadapt to the windy and dusty natural environment of the North of China.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a precision air conditioner with an indirect evaporativeunit according to an embodiment of the present invention.

FIG. 2 is a perspective view of the gas-gas heat exchanger shown in FIG.1.

FIG. 3 shows a cross-section of a gas-gas heat exchanger.

FIG. 4 shows another shape of the cross-section of the gas-gas heatexchanger.

FIG. 5 shows another shape of the cross-section of the gas-gas heatexchanger.

FIG. 6 shows another shape of the cross-section of the gas-gas heatexchanger.

REFERENCE NUMERALS

11-internal circulation air inlet, 12-heat exchanger internalcirculation air inlet, 13-heat exchanger internal circulation airoutlet, 14-internal circulation air outlet, 21-external circulation airinlet, 22-heat exchanger external circulation air inlet, 23-heatexchanger external circulation air outlet, 24-external circulation airoutlet, 31-condenser air inlet, 32-condenser air outlet, 41-externalcirculation air intake passage, 42-heat exchanger external circulationpassage, 43-external circulation air exhaust passage, 44-heat exchangerinternal circulation passage, 45-internal circulation air exhaustpassage, 46-condenser air exhaust passage; 51-evaporator, 52-condenser,53-compressor, 54-gas filter module, 55-gas humidification module,56-gas-gas heat exchanger, 61-internal circulation fan, 62-externalcirculation fan, 63-condenser fan.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described more fully hereinafter withreference to the accompanying drawings. Preferred embodiments of theinvention are shown in the drawings. However, the invention may be madein many different forms and is not limited to the embodiments describedherein. These embodiments are provided to explain the disclosure of theinvention in detail.

It should be noted that when an element is referred to as being “fixed”to another element, it may refer to that the element is directlyarranged on the other element, or that there is an intermediate elementarranged between them. When an element is referred to as being“connected” to another element, it may refer to that the element isdirectly connected to the other element, or that there is anintermediate element arranged between them.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by those skilled in theart. The terminology is used to describe embodiments in the description,but is not intended to limit the invention.

As shown in FIG. 1, the precision air conditioner with an indirectevaporative unit according to the embodiment of the present inventioncomprises a gas-gas heat exchanger 56, an internal circulation fan 61,an external circulation fan 62, a gas filter module 54, a gashumidification module 55, an evaporator 51, a condenser 52, a compressor53, a condenser fan 63, and an air conditioner enclosure in which theentire precision air conditioner is enclosed. The air conditionerfurther comprises an internal circulation air inlet 11, heat exchangerinternal circulation air inlet 12, heat exchanger internal circulationair outlet 13, internal circulation air outlet 14, external circulationair inlet 21, heat exchanger external circulation air inlet 22, heatexchanger external circulation air outlet 23, external circulation airoutlet 24, condenser air inlet 31, and condenser air outlet 32. Theinternal circulation fan 61 is arranged below the heat exchanger 56, andthe external circulation fan 62 is arranged above the heat exchanger 56.The condenser fan 63 is arranged above or below the condenser 52 andcommunicates with the external circulation air intake passage 41. Theinternal air enters the precision air conditioner from the internalcirculation air inlet 11, and is exhausted to the interior from theinternal circulation air outlet 14. The external air enters theprecision air conditioner from the external circulation air inlet 21,and is exhausted to the exterior from the external circulation airoutlet 24 and condenser air outlet 32.

In this embodiment, the external air refers to air that enters theexterior through the external circulation air inlet, and the internalair refers to air that enters the interior through the internalcirculation air inlet.

In this embodiment, a complete external air circulation is as follows.The external air is filtered by the gas filter module 54 and humidifiedby the gas humidification module 55 and then enters the externalcirculation air intake passage 41. Subsequently, the external air entersthe heat exchanger external circulation passage 42 in the gas-gas heatexchanger 56. Heat is transferred to the internal air through the wall.The external air then enters the external circulation air exhaustpassage 43 and is exhausted to the exterior by the external circulationfan 62.

A complete internal air circulation is as follows. The internal airenters the heat exchanger internal circulation passage 44 in the gas-gasheat exchanger 56 from the internal circulation air inlet 11. Heat istransferred to the external air through the wall. The internal air iscooled by the evaporator 51 and then enters the internal circulation airexhaust passage 45 and is exhausted to the interior by the internalcirculation fan 61.

The gas-gas heat exchanger 56 is a type of gas-gas heat exchanger havingdividing walls, in which the heat exchanger external circulation passage42 and the heat exchanger internal circulation passage 44 are completelyseparated by the heat exchange plates of the gas-gas heat exchanger 56,such that heat is transferred between the external air and the internalair through the heat exchange plates.

A complete condenser cooling gas-circulation is as follows. The externalair is filtered by the gas filter module 54 and humidified by the gashumidification module 55 and then enters the external circulation airintake passage 41. Subsequently, the external air enters the condenser52, such that heat is transferred to the condenser. The external airenters the condenser air exhaust passage 46 and is then exhausted to theexterior by the condenser fan 63. Generally, after the exterior airpasses through the gas humidification module 55, its temperature islowered to become low temperature exterior air, so that the operatingtemperature of the condenser according to the embodiment is lower thanthe temperature of the exterior air, resulting in a higher coolingefficiency of mechanical refrigeration.

As shown in FIG. 2, the gas-gas heat exchanger 56 is a type of gas-gasheat exchanger having dividing walls, and includes heat exchangerplates, a heat exchanger external circulation air inlet 22, a heatexchanger external circulation air outlet 23, a heat exchanger internalcirculation air inlet 12 and heat exchanger internal circulation airoutlet 13, wherein the heat exchanger external circulation passage 42and the heat exchanger internal circulation passage 44 are spaced andformed by the heat exchanger plates arranged to be spaced. It is furtherprovided with air inlet and outlet. The internal air goes through theheat exchanger internal circulation passage 44 in the heat exchanger,entering from the heat exchanger internal circulation air inlet 12 andexiting from the heat exchanger internal circulation air outlet 13. Theexternal air goes through the heat exchanger external circulationpassage 42 in the heat exchanger, entering from the heat exchangerexternal circulation air inlet 22 and exiting from the heat exchangerexternal circulation air outlet 23.

In an instance, temperature of the internal circulation return air for adata center employing the present precision air conditioner is 35° C.,while temperature of the supply air should be controlled at 23° C.indoors. In summer, when temperature of the external air is 37° C. andthe relative humidity is 50% (the wet bulb temperature is 28° C.), theuse of indirect evaporative cooling alone may not cool the innercirculation return air to the expected 23° C. Therefore, it is necessaryto operate the compressor for secondary cooling. The specific workingprocess is as follows. When entering the external circulation passage ofthe precision air conditioner, the external air is humidified throughthe gas humidification module and achieves a relative humidityapproximate to 100% and a gas temperature approximate to 28° C. Afterpassing through the gas-gas heat exchanger, temperature of the externalair rises to 34.3° C. In the internal circulation, the internal air at35° C. is cooled to 28.7° C. after passing through the gas-gas heatexchanger, and then further cooled to 23° C. by the evaporator. In suchprocess, the relative cooling capacity is approximately (35° C.-28.7°C.)/(35° C.-23° C.)=52.5%, that is, indirect evaporative coolingaccounts for 52.5% of the total cooling load of this data center.Therefore, mechanical refrigeration needs to provide only 47.5% of thecooling capacity. The energy efficiency of a compressor operating underthese conditions is much higher than its energy efficiency at full load.Alternatively, when temperature of the external air is 30° C. and therelative humidity is 40% (the wet bulb temperature is 20° C.), theexternal air is humidified through the gas humidification module andachieves a relative humidity approximate to 100% and a gas temperatureapproximate to 20° C. After passing through the gas-gas heat exchanger,temperature of the external air rises to 33.5° C. The internal air at35° C. is cooled to 21.5° C. after passing through the gas-gas heatexchanger. In this case, the indirect evaporative cooling satisfies thecooling requirement of the internal air, so that it is not necessary tooperate the compressor.

The present invention provides a new apparatus by combining two ways ofcooling, including mechanical refrigeration and indirect evaporativecooling. The apparatus may cool the air exhausted from the server bymeans of indirect evaporative cooling in spring, autumn and winter. Insummer, indirect evaporative cooling is employed for preliminarycooling, and mechanical cooling is employed to cool the air if the airdoes not reach the expected 23° C., thus saving energy. It would bepossible for the data centers in most of the area north of the YangtzeRiver in China that the compressor runs no more than 3 months, whichwill greatly improve the energy efficiency throughout the year. Inaddition, in summer when the variable-frequency compressor operates, themechanical refrigeration efficiency may be greatly improved due to thelow-load operation of the compressor and the use of indirect evaporativecondenser.

In one embodiment, as shown in FIG. 1, heat exchanger externalcirculation air inlet 22, heat exchanger external circulation air outlet23, heat exchanger internal circulation air inlet 12, heat exchangerinternal circulation air outlet 13 are respectively arranged at thebottom-right corner, upper side, at the top-left corner and lower sideof the gas-gas heat exchanger 56. In other embodiments, the inlet andoutlet for the internal air and the external air may be arrangedelsewhere, as long as the internal air and the external air flow in acounter-flow manner inside the gas-gas heat exchanger 56. The so-calledcounter-flow manner means that the heat exchanger internal circulationpassage 44 and the heat exchanger external circulation passage 42 arearranged parallel to each other.

In the present invention, the gas-gas heat exchanger 56 may have othershapes as shown in FIGS. 3, 4, 5, and 6. It comprises heat exchangerplates, heat exchanger external circulation air inlet 22, heat exchangerexternal circulation air outlet 23, heat exchanger internal circulationair inlet 12, heat exchanger internal circulation air outlet 13, heatexchanger external circulation passage 42 and heat exchanger internalcirculation passage 44.

The gas-gas heat exchanger shown in FIG. 3 is a cuboid having arectangular cross section, wherein the heat exchanger externalcirculation passage 42 and heat exchanger internal circulation passage44 are arranged in a counter-flow manner inside the heat exchanger, andare arranged in a cross-flow manner at the inlet or outlet.

As shown in FIGS. 4 and 5, the gas-gas heat exchanger has a hexagonal ora hexagonal cross section, wherein the heat exchanger externalcirculation passage 42 and heat exchanger internal circulation passage44 are arranged in a counter-flow manner inside the heat exchanger, andare arranged in a cross-flow manner at the inlet or outlet.

As shown in FIG. 6, the gas-gas heat exchanger has a cross section of acombination of two quadrangles, wherein the heat exchanger externalcirculation passage 42 and heat exchanger internal circulation passage44 are arranged in a cross-flow manner inside the heat exchanger, andare arranged in a cross-flow manner at the inlet or outlet.

Preferably, the gas-gas heat exchanger 56 comprises a cleaning nozzle tospray liquid, by which the interior of the heat exchanger 56 can beperiodically cleaned to prevent clogging of the heat exchanger externalcirculation passage.

Preferably, the gas filter module 54 further comprises an automatic dustremoval assembly for periodically removing dust from the filter screen,by which the gas filter module can be dusted periodically withoutmanually changing the filter.

Preferably, the gas humidification module 55 further comprises avariable-frequency water pump, wherein the water pressure is adjusted byadjusting working load of the variable-frequency water pump during theoperation of the air conditioning system. The gas humidification modulefurther comprises a plurality of sets of nozzles, each of whichcorresponds to a specific start-up pressure. The nozzle will work whenthe pressure is greater than or equal to the start-up pressure of thecorresponding nozzle. With the plurality of sets of nozzles, the nozzlesmay work normally in a wide range of water pressure.

Preferably, the external circulation air exhaust passage 43 of the airconditioner enclosure is curved, and the external circulation air isdistributed to both sides of the apparatus and exhausted to theexterior.

Preferably, the compressor 53 is a variable-frequency compressor, andthe amount of compression can be changed by controlling the frequency ofthe compressor, thereby achieving precise control of the coolingcapacity and low-load operation of the compressor.

Preferably, both the internal circulation fan 61 and the externalcirculation fan 63 are centrifugal electronically commutated fans. Theflow direction changes by 90 degrees or nearly 90 degrees after the airpasses through the fan. The nearly 90 degrees turn of the airflow makesthe entire precision air conditioner more compact and space saving.

Any combinations of the technical features of the above embodiments maybe allowable. All combinations of the technical features of the aboveembodiments will not described in detail. However, as long as there isno contradiction in the combination of these technical features, it isconsidered to be within the scope of the invention.

It should be noted that the above embodiments are only used to explainthe preferred technical solutions of the present invention, and are notlimited thereto. Although the present invention is described in detailwith reference to the preferred embodiments, those skilled in the artshould understand that the modifications or equivalent substitutions ofthe present invention are not intended to be excluded from the scope ofthe invention.

We claim:
 1. A precision air conditioner with an indirect evaporativeunit, comprising: a gas-gas heat exchanger, an external circulation fan,an internal circulation fan, a gas filter module, a gas humidificationmodule, an evaporator, a condenser, a condenser fan, a compressor, anair conditioner enclosure; wherein the gas-gas heat exchanger isprovided with a heat exchanger internal circulation air inlet, a heatexchanger internal circulation air outlet, a heat exchanger externalcirculation air inlet, a heat exchanger external circulation air outlet,a heat exchanger internal circulation passage, and a heat exchangerexternal circulation passage and heat exchanger plates; the gas-gas heatexchanger is a type of gas-gas heat exchanger having dividing walls, andthe heat exchanger plates are arranged to be spaced to form the heatexchanger internal circulation passage and the heat exchanger externalcirculation passage; heat is transferred between external air andinternal air through the heat exchanger plates of the gas-gas heatexchanger; wherein the air conditioner enclosure is arranged around theprecision air conditioner with an indirect evaporative unit; the airconditioner enclosure is provided with an internal circulation airinlet, an internal circulation air exhaust passage, an externalcirculation air inlet, an external circulation air intake passage and anexternal circulation air exhaust passage; wherein the internalcirculation air inlet is connected to the heat exchanger internalcirculation air inlet, and the external circulation air intake passageis connected to the heat exchanger external circulation air inlet;wherein the external circulation fan is arranged above the gas-gas heatexchanger; wherein the internal circulation fan is arranged below thegas-gas heat exchanger; wherein the gas filter module, which isconnected with the external circulation air inlet, is arranged in theexternal circulation air intake passage; the gas filter module isarranged perpendicularly or substantially perpendicularly; wherein thegas humidification module is arranged between the gas filter module andthe gas-gas heat exchanger; wherein the evaporator is arranged in theinternal circulation air exhaust passage below the gas-gas heatexchanger; wherein the condenser is arranged below or above the externalcirculation air intake passage and communicates with the externalcirculation air intake passage; wherein the condenser fan is arrangedbelow or above the condenser; wherein the compressor is connected to theevaporator and the condenser, wherein the precision air conditioner hasa complete external air circulation as follows: the external air goesthrough the gas filter module and enters the external circulation airintake passage, and then enters the heat exchanger external circulationpassage after being humidified by the gas humidification module; heat istransferred between the external air and the internal air flowing in theheat exchanger internal circulation passage through the heat exchangerplates, and then the external air enters the external circulation airexhaust passage, and then is exhausted to the exterior by the externalcirculation fan; wherein the precision air conditioner has a completeinternal air circulation as follows: the internal air enters the heatchanger internal circulation passage from the internal circulation airinlet; heat is transferred between the internal air and the external airflowing in the heat exchanger external circulation passage through theheat exchanger plates; the internal air goes through the evaporator andthen is cooled; the internal air then enters the internal circulationair exhaust passage, and then is exhausted to the interior by theinternal circulation fan; wherein the precision air conditioner has acomplete condenser cooling gas-circulation as follows: the external airgoes through the gas filter module and enters the external circulationair intake passage, and then enters the condenser after being humidifiedby the humidification module; heat is transferred between the externalair and the condenser, and then the external air is exhausted to theexterior by the condenser fan.
 2. The precision air conditioner with anindirect evaporative unit according to claim 1, wherein the gas-gas heatexchanger is a cuboid having a rectangular cross section; and whereinthe heat exchanger external circulation air outlet is arranged on thetop of the gas-gas heat exchanger, the heat exchanger internalcirculation air outlet is arranged on the bottom of the gas-gas heatexchanger, the heat exchanger external circulation air inlet is arrangedat the bottom-right corner of the gas-gas heat exchanger, and the heatexchanger internal circulation air inlet is arranged at the top-leftcorner of the gas-gas heat exchanger.
 3. The precision air conditionerwith an indirect evaporative unit according to claim 1, wherein thegas-gas heat exchanger has a hexagonal cross section; and wherein thegas-gas heat exchanger employs a counter-flow arrangement in the middleportion and a cross-flow arrangement at the inlet or outlet for theexternal air and the internal air.
 4. The precision air conditioner withan indirect evaporative unit according to claim 1, wherein the gas-gasheat exchanger has a pentagonal cross section; and wherein the gas-gasheat exchanger employs a counter-flow arrangement in the middle portionand a cross-flow arrangement at the inlet or outlet for the external airand the internal air.
 5. The precision air conditioner with an indirectevaporative unit according to claim 1, wherein the gas-gas heatexchanger has a cross section of a combination of two quadrangles; andwherein the gas-gas heat exchanger employs a cross-flow arrangement inthe middle portion and at the inlet or outlet for the external air andthe internal air.
 6. The precision air conditioner with an indirectevaporative unit according to claim 1, wherein a cleaning nozzle tospray liquid is arranged inside the gas-gas heat exchanger.
 7. Theprecision air conditioner with an indirect evaporative unit according toclaim 1, wherein the gas filter module comprises an automatic dustremoval assembly for periodically removing dust from a filter screen. 8.The precision air conditioner with an indirect evaporative unitaccording to claim 1, wherein the gas humidification module furthercomprises a variable-frequency water pump, and water pressure isadjusted by adjusting working load of the variable-frequency water pumpduring the operation of an air conditioning system; wherein the gashumidification module further comprises a plurality of sets of nozzles,each of which corresponds to a specific start-up pressure, and thenozzle will work when the pressure is greater than or equal to thestart-up pressure of the corresponding nozzle.
 9. The precision airconditioner with an indirect evaporative unit according to claim 1,wherein the external circulation air exhaust passage of the airconditioner enclosure is curved, and the external circulation air isdistributed to both sides of the air conditioner enclosure and exhaustedto exterior.
 10. The precision air conditioner with an indirectevaporative unit according to claim 1, wherein the internal circulationfan and the external circulation fan are centrifugal electronicallycommutated fans; and wherein flow direction changes by 90 degrees ornearly 90 degrees after the air passes through the fan.